Sinister beauty concealing corruption (8)
I believe the answer is:
devilish
'sinister' is the definition.
(thesaurus)
'beauty concealing corruption' is the wordplay.
'beauty' becomes 'dish' (slang term for an attractive person).
'concealing' is an insertion indicator.
'corruption' becomes 'evil' (I've seen this in another clue).
'dish' enclosing 'evil' is 'DEVILISH'.
(Other definitions for devilish that I've seen before include "naughty" , "Very wicked" , "Mischievous; rakish" , "Very difficult to deal with" , "like Screwtape" .)